A method of supplying electric power to a power-receiving coil of an electric vehicle is disclosed in Patent Document 1 described below. In Patent Document 1, the power-receiving coil is provided at a lower surface of the electric vehicle, and a power-supplying coil is provided in a stop area of the electric vehicle. A position of the power-receiving coil is aligned with a position of the power-supplying coil so that the power-receiving coil and the power-supplying coil are opposite to each other by positioning of the electric vehicle. In this state, alternating-current electric power is supplied to the power-supplying coil. Accordingly, electric power is wirelessly supplied from the power-supplying coil to the power-receiving coil. The power supplied to the power-receiving coil is stored in a battery provided in the electric vehicle.
As described above, in order to supply the supply electric power from the power-supplying coil provided in the stop area to the power-receiving coil provided on the electric vehicle, the position of the power-supplying coil should be aligned with the position of the power-receiving coil.
For this reason, in Patent Document 1, a transmission coil for communication is installed in an internal space of the power-receiving coil, and a reception coil for communication is installed in an internal space of the power-supplying coil. When the position of transmission coil is aligned with the position of the reception coil, the position of the power-receiving coil is aligned with the position of the power-supplying coil.
According to the above-mentioned configuration, in Patent Document 1, as described below, the position of the power-receiving coil is aligned with the position of the power-supplying coil. An electromagnetic wave from a transmission coil is received in a reception coil while the position of the electric vehicle is varied by driving the electric vehicle. When level of the electromagnetic wave received in the reception coil exceeds a threshold value, the electric vehicle is stopped. In this state, the position of the power-receiving coil is aligned with the position of the power-supplying coil.